U.S. patent application number 10/869177 was filed with the patent office on 2005-06-02 for system for tracking object locations using self-tracking tags.
Invention is credited to Arman, Farshid, Meyer, Heinrich, Paulsen, Torsten.
Application Number | 20050116823 10/869177 |
Document ID | / |
Family ID | 34623296 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050116823 |
Kind Code |
A1 |
Paulsen, Torsten ; et
al. |
June 2, 2005 |
System for tracking object locations using self-tracking tags
Abstract
An object tracking system includes a plurality of tags. Each tag
includes a mechanism for transmitting a triangulation signal and a
position signal that is indicative of a change of position of the
respective tag in a time period since a respective reset event. A
plurality of triangulation stations receive the triangulation
signals from the tags. At least one antenna receives the position
signals from the tags. A computer is coupled to the triangulation
stations and to the antenna. The computer is programmed to switch
between (a) a first tag location algorithm to determine a current
location of one of the tags using a differential time of arrival
procedure based on the triangulation signal, and (b) a second tag
location algorithm to determine a current location of the tag based
on the position signal transmitted by the tag and a previous known
location of the tag.
Inventors: |
Paulsen, Torsten; (Feucht,
DE) ; Meyer, Heinrich; (Nuernberg, DE) ;
Arman, Farshid; (Lafayette, CA) |
Correspondence
Address: |
Siemens Corporation
Attn: Elsa Keller, Legal Administrator
Intellectual Property Department
170 Wood Avenue South
Iselin
NJ
08830
US
|
Family ID: |
34623296 |
Appl. No.: |
10/869177 |
Filed: |
June 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60527110 |
Dec 3, 2003 |
|
|
|
Current U.S.
Class: |
340/539.13 ;
340/572.1; 342/126; 701/472 |
Current CPC
Class: |
G01S 2205/002 20130101;
G01S 5/06 20130101; G08B 13/2454 20130101; G01S 5/0036 20130101;
G08B 13/2462 20130101 |
Class at
Publication: |
340/539.13 ;
340/572.1; 342/126; 701/216 |
International
Class: |
G08B 001/08 |
Claims
What is claimed is:
1. A system comprising: a plurality of tags, each tag including
means for transmitting a triangulation signal and a position
signal, the position signal indicative of a change of position of
the respective tag in a time period since a respective reset event;
a plurality of triangulation stations for receiving the
triangulation signals from the tags; at least one antenna for
receiving the position signals from the tags; and a computer
coupled to the triangulation stations and to the at least one
antenna, the computer programmed to switch between: (a) a first tag
location algorithm in which the computer determines a current
location of one of the tags using a differential time of arrival
procedure based on the triangulation signal transmitted by said one
of the tags and received by at least some of the triangulation
stations; and (b) a second tag location algorithm in which the
computer determines a current location of said one of the tags
based on the position signal transmitted by said one of the tags
and a previous known position of said one of the tags.
2. A system according to claim 1, wherein the computer is a server
computer installed at a fixed location.
3. A system according to claim 1, further comprising: at least one
client computer coupled to the server computer to allow a user of
the client computer to query the server computer as to a current
location of at least one of the tags.
4. A system according to claim 1, wherein each of the tags
includes: at least one sensor including at least one acceleration
sensor; and generating means for generating said position signal
based on information from said at least one sensor.
5. A system according to claim 4, further comprising: reset means
for indicating to said generating means occurrence of said
respective reset event.
6. A system according to claim 4, wherein the at least one sensor
includes a gyroscope.
7. A system according to claim 1, further comprising: at least one
interrogation gate coupled to the computer.
8. A method comprising: (a) selectively employing a differential
time of arrival procedure to determine a current location of a tag
based on a triangulation signal transmitted by the tag; and (b)
determining a current location of the tag based on a position
signal transmitted by the tag and a previous known location of the
tag.
9. A method according to claim 8, further comprising: receiving
from the tag an identification code that uniquely identifies the
tag.
10. A method according to claim 8, wherein said position signal is
indicative of a change of position of said tag in a time period
since a reset event.
11. A method according to claim 8, wherein said position signal
includes data calculated based at least in part on input signals
from at least one acceleration sensor in the tag.
12. A tag comprising: a housing; first transmitting means in said
housing for transmitting a triangulation signal; at least one
sensor in the housing, said at least one sensor including at least
one acceleration sensor; calculating means in said housing for
receiving sensor information from said at least one sensor and for
calculating position data for the tag based on the sensor
information; and second transmitting means in said housing for
selectively transmitting said position data calculated by said
calculating means.
13. A tag according to claim 12, wherein the first transmitting
means transmits as part of the triangulation signal an
identification code that uniquely identifies the tag.
14. A tag according to claim 13, further comprising: response means
in said housing for receiving an interrogation signal from an
interrogation gate and for transmitting said identification code in
response to receipt of said interrogation signal.
15. A tag according to claim 14, further comprising: reset means
coupled to said calculating means for receiving a reset signal; and
wherein said calculating means calculates said position data to
indicate movement of the tag from a time when the reset means
received the reset signal.
16. A tag according to claim 15, wherein said interrogation signal
is said reset signal.
17. A tag according to claim 12, further comprising: reset means
coupled to said calculating means for receiving a reset signal; and
wherein said calculating means calculates said position data to
indicate movement of the tag from a time when the reset means
received the reset signal.
18. A tag according to claim 12, wherein: said calculating means
calculates a current direction of motion of the tag based on the
sensor information; and said second transmitting means transmits to
an interrogation gate data indicative of the current direction of
motion calculated by said calculating means.
19. A tag according to claim 12, wherein said second transmitting
means includes a radio frequency transmitter.
20. A tag comprising: a housing; response means in said housing for
receiving an interrogation signal from an interrogation gate and
for transmitting, in response to receipt of said interrogation
signal, an identification code that uniquely identifies the tag; at
least one sensor in the housing, said at least one sensor including
at least one acceleration sensor; and calculating means in said
housing for receiving sensor information from said at least one
sensor and for calculating a current direction of motion of the tag
based on the sensor information; wherein said response means
transmits to the interrogation gate data indicative of the current
direction of motion calculated by said calculating means.
21. A method comprising: determining a current location of a tag
based on a signal from an interrogation gate when the tag is in
proximity to the interrogation gate; and when the tag is not in
proximity to any interrogation gate, determining a current location
of the tag based on a position signal transmitted by the tag and a
previous known location of the tag.
22. A method according to claim 21, further comprising: receiving
from the tag an identification code that uniquely identifies the
tag.
23. A method according to claim 21, wherein said position signal is
indicative of a change of position of said tag in a time period
since a reset event.
24. A method according to claim 21, wherein said position signal
includes data calculated based at least in part on input signals
from at least one acceleration sensor in the tag.
25. A method according to claim 21, further comprising: selectively
employing a differential time of arrival procedure to determine a
current location of the tag based on a triangulation signal
transmitted by the tag.
26. A system comprising: a plurality of tags, each tag including
means for transmitting a response signal and a position signal, the
position signal indicative of a change of position of the
respective tag in a time period since a respective reset event; a
plurality of interrogation gates; at least one antenna for
receiving the position signals from the tags; and a computer
coupled to the interrogation gates and to the at least one antenna,
the computer programmed to: determine a current location of one of
said tags based on a signal from one of the interrogation gates at
a time when said one of the tags is in proximity to said one of the
interrogation gates; and determine, at a time when said one of the
tags is not in proximity to any of the interrogation gates, a
current location of said one of the tags based on the respective
position signal transmitted by said one of the tags and a previous
known location of said one of the tags.
27. A system according to claim 26, wherein the respective reset
event is interrogation of the respective tag by one of the
interrogation gates.
28. A system according to claim 26, wherein the computer is a
server computer installed at a fixed location.
29. A system according to claim 28, further comprising: at least
one client computer coupled to the server computer to allow a user
of the client computer to query the server computer as to a current
location of at least one of the tags.
30. A system according to claim 26, wherein each of the tags
includes: at least one sensor including at least one acceleration
sensor; and means for generating said position signal based on
information from said at least one sensor.
31. A system according to claim 26, wherein: each of said plurality
of tags includes means for transmitting a triangulation signal; the
system further comprises a plurality of triangulation stations for
receiving the triangulation signals from the tag signal; and said
computer is further programmed to determine a current location of
said one of the tags using a differential time of arrival procedure
based on the triangulation signal transmitted by said one of the
tags and received by at least some of the triangulation
stations.
32. A system according to claim 31, wherein said position signal
transmitted by said one of the tags is indicative of a change of
position of said one of the tags in a time period since a
respective reset event.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to U.S. Provisional Patent Application Ser. No. 60/527,110,
entitled "Autarkic Object Positioning and Locating System with
MEMS-based Devices", filed in the name of Paulsen et al. on Dec. 3,
2003, the contents of which are hereby incorporated by reference in
their entirety for all purposes.
BACKGROUND
[0002] The present disclosure relates generally to systems and tags
used for tracking the locations of objects, and is more
particularly concerned with an object tracking system in which more
than one type of object tracking procedure is employed.
[0003] It can be highly advantageous in the environment of a
factory to be able to keep track of the current locations of
certain objects. For example, it may be desirable to keep track of
the locations of tools, production equipment, inventory and/or the
items being produced in the factory. Object location tracking is
also potentially applicable to other environments, such as
warehouses, vehicle parking lots, railroad yards, container
terminals, and the like.
[0004] FIG. 1 is a schematic plan view representation of a
conventional object tracking system 100. The object tracking system
100 is installed in a factory facility 102. The object tracking
system 100 utilizes tags 104 (represented in the drawing by
octagonal symbols that also serve to represent objects, not
separately shown, to which the tags are affixed to permit tracking
of the objects).
[0005] The object tracking system 100 utilizes two different
procedures--proximity detection and triangulation--to track the
tags 104. Interrogation gates 106 are used for proximity detection,
and triangulation stations 108 allow tag locations to be determined
by triangulation. Another significant element of the system 100,
but not shown in the drawing, is a central computer that is coupled
by signal paths (also not shown) to the interrogation gates 106 and
triangulation stations 108.
[0006] In accordance with conventional practices, a tag 104 that is
in proximity to an interrogation gate 106 receives an interrogation
signal from the interrogation gate and responds to the
interrogation signal by transmitting a response signal that
includes a tag identification code that uniquely identifies the
tag. The interrogation gate then effectively reports to the central
computer that the particular tag is at the interrogation gate. The
interaction between the tag and the interrogation gate may be in
accordance with conventional RFID (radio frequency identification)
practices. In other variations, the interrogation gate may read a
barcode or the like from the tag.
[0007] The tags 104 send out signals at brief regular intervals
which are received by triangulation station 108. By using the
triangulation stations 108, the central computer utilizes a
triangulation procedure to determine the location of tags that are
not in proximity to one of the interrogation gates 106. More
specifically, the central computer may use a differential time of
arrival (DTOA) procedure in which a tag ID signal transmitted by a
tag 104 is received by three or more of the triangulation stations
108. Differences in the timing at which the tag ID signal is
received at each triangulation station are used by the central
computer to calculate the location of the tag, based on the
locations of the stations 108 which received the tag ID signal. For
example, in FIG. 1, a tag ID signal transmitted by tag 104-1 is
received by line-of-sight at triangulation stations 108-1, 108-2,
108-3, thereby allowing the location of tag 104-1 to be determined
by triangulation. Similarly, a tag ID signal transmitted by tag
104-2 is received by triangulation stations 108-4, 108-5, 108-6 so
that the location of tag 104-2 can be determined by
triangulation.
[0008] The "MOBY R" object locating system available from Siemens A
G, an assignee hereof, is an example of a system that employs DTOA
to locate objects.
[0009] In some examples of a conventional object tracking system,
the number of tags may be in the thousands, and the number of
interrogation gates and/or triangulation stations may be in the
dozens.
[0010] An object tracking system as illustrated in FIG. 1 often
operates effectively to achieve its intended purposes. However, in
some cases such systems may exhibit drawbacks that it would be
desirable to address. For example, triangulation by DTOA requires
line-of-sight transmission from a tag to three or more
triangulation stations and thus works best in open, unobstructed
areas. Disadvantageously, some factory environments may have a
significant number of obstructions to tag ID signal transmission,
such as the obstructions 110 shown in FIG. 1. When obstructions are
present, it is usually necessary to provide an increased number of
triangulation stations to avoid "dead spots" in which tags cannot
be detected by triangulation. This increases the cost of the
tracking system. Furthermore, the presence of obstructions
increases the amount of time required for planning the system and
determining the locations at which triangulation stations are to be
installed. This too increases the cost of the system, and also
increases the time required to deploy the system.
[0011] Moreover, "temporary" obstructions, such as loaded pallets,
trucks, forklifts, etc., may interfere with triangulation
capabilities of the system. Consider for example the case of tag
104-3 shown in FIG. 1. It is assumed that a temporary obstruction
is placed as indicated in phantom at 112, blocking the
line-of-sight transmission path from tag 104-3 to triangulation
station 108-4. As a result, line-of-sight transmission is possible
from tag 104-3 only to two triangulation stations, namely stations
108-7 and 108-8. Consequently, the location of tag 104-3 cannot
currently be determined by DTOA.
[0012] Even in the absence of such problems, reflections of tag ID
signal transmissions may adversely affect performance of the DTOA
procedure.
[0013] In simpler object tracking systems, only interrogation gates
are employed. However, in such systems, the location of an object
is known only when it is in proximity to an interrogation gate. If,
for example, a gate is provided at the entrance to a large enclosed
area (e.g., a warehouse or parking lot), it may be possible to
determine that an object is in the enclosed area, but finding the
object within that area may be difficult, and is not aided by the
object tracking system.
SUMMARY
[0014] Apparatus and methods are therefore presented for an
improved object tracking system.
[0015] According to some embodiments, a system includes a plurality
of tags. Each tag includes one or more mechanisms for transmitting
a triangulation signal and a position signal. The position signal
is indicative of a change of position of the respective tag in a
time period since a respective reset event. The system also
includes a plurality of triangulation stations for receiving the
triangulation signals from the tags. Also included in the system is
at least one antenna for receiving the position signals from the
tags. The system further includes a computer coupled to the
triangulation stations and to the at least one antenna. The
computer is programmed to switch between (a) a first tag location
algorithm in which the computer determines a current location of
one of the tags using a differential time of arrival procedure
based on the triangulation signal transmitted by the tag in
question, the triangulation signal being received by at least some
of the triangulation stations, and (b) a second tag location
algorithm in which the computer determines a current location of
the tag in question based on the position signal transmitted by the
tag and a previous known location of the tag.
[0016] According to some embodiments, a method includes (a)
selectively employing a differential time of arrival procedure to
determine a current location of a tag based on a triangulation
signal transmitted by the tag, and (b) determining a current
location of the tag based on a position signal transmitted by the
tag and a previous known location of the tag. The latter
determination may be performed at all times but used only at a time
when it is determined that the triangulation signal from the tag is
not received in a manner to permit performing the differential time
of arrival procedure according to some predetermined metrics.
[0017] According to some embodiments, a tag includes a housing and
a first transmitting mechanism in the housing for transmitting a
triangulation signal. The tag also includes at least one sensor in
the housing. The at least one sensor includes at least one
acceleration sensor. Also included in the tag is a calculating
mechanism in the housing to receive sensor information from the at
least one sensor and for calculating position data for the tag
based on the sensor information. The tag further includes a second
transmitting mechanism in the housing to selectively transmit the
position data calculated by the calculating mechanism.
[0018] According to some embodiments, a tag includes a housing and
a response mechanism in the housing. The response mechanism is for
receiving an interrogation signal from an interrogation gate and
for transmitting, in response to receipt of the interrogation
signal, an identification code that uniquely identifies the tag.
The tag also includes at least one sensor in the housing. The at
least one sensor include at least one acceleration sensor. Also
included in the tag is a calculating mechanism in the housing. The
calculating mechanism is for receiving sensor information from the
at least one sensor and for calculating a current direction of
motion of the tag based on the sensor information. The response
mechanism transmits to the interrogation gate data indicative of
the current direction of motion calculated by the calculating
mechanism.
[0019] According to some embodiments, a method includes determining
a current location of a tag based on a signal from an interrogation
gate when the tag is in proximity to the interrogation gate, and,
at a time when the tag is not in proximity to any interrogation
gate, determining a current location of the tag based on a position
signal transmitted by the tag and a previous known location of the
tag.
[0020] According to some embodiments, a system includes a plurality
of tags. Each tag includes at least one mechanism for transmitting
a response signal and a position signal. The position signal is
indicative of a change of position of the respective tag in a time
period since a respective reset event. The system also includes a
plurality of interrogation gates, and at least one antenna for
receiving the position signals from the tags. The system further
includes a computer coupled to the interrogation gates and to the
at least one antenna. The computer is programmed to determine a
current location of one of the tags based on a signal from one of
the interrogation gates at a time when the tag in question is in
proximity to the interrogation gate in question. The computer is
further programmed to determine, at a time when the tag is not in
proximity to any of the interrogation gates, a current location of
the tag in question based on the respective position signal
transmitted by the tag and a previous known location of the
tag.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Further aspects of the instant system will be more readily
appreciated upon review of the detailed description of the
preferred embodiments included below when taken in conjunction with
the accompanying drawings, of which:
[0022] FIG. 1 is a schematic plan view representation of a
conventional object tracking system;
[0023] FIG. 2 is a schematic plan view representation of an object
tracking system in accordance with some aspects of the
invention;
[0024] FIG. 3 is a schematic plan view representation of an
alternative embodiment of the object tracking system of FIG. 2;
[0025] FIG. 4 is a diagram that illustrates components of the
object tracking system of FIG. 2 or 3;
[0026] FIG. 5 is block diagram of a typical tag that may be
employed in accordance with some embodiments of the invention as
part of the object tracking system according to one or more of
FIGS. 2-4;
[0027] FIG. 6 is a block diagram of a server computer that may be
employed as part of the object tracking system according to one or
more of FIGS. 2-4;
[0028] FIG. 7 is a flow chart that illustrates a process that may
be performed in accordance of some embodiments of the invention by
the tag of FIG. 5; and
[0029] FIG. 8 is a flow chart of a process that may be performed in
accordance with some embodiments of the invention by the server
computer of FIG. 6.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0030] According to some embodiments, an object tracking system
utilizes tags that include acceleration sensors and/or other
sensors, such as gyroscopes, that allow the tag to track its own
changes in position and to store information indicative of the
changes in position of the tag. The tag position change information
may be uploaded to a central server computer from the tag. The
central server computer may use the position change information
uploaded from the tag, plus a previous known location for the tag,
to determine the tag's current location. At other times, the object
tracking system may utilize DTOA or a signal from an interrogation
gate to determine the current location of the tag. The system may
switch back and forth between using the position information from
the tag and using DTOA, depending on whether the tag is
satisfactorily located for DTOA.
[0031] As used herein and in the appended claims, "triangulation
signal" refers to a signal transmitted by a tag to a plurality of
fixed receiving stations (e.g., triangulation stations) to allow a
calculating device (e.g., a computer) coupled to the receiving
stations to calculate the current location of the tag by a
differential time of arrival (DTOA) technique.
[0032] As used herein and in the appended claims, "triangulation
station" refers to a station adapted to receive a triangulation
signal.
[0033] As used herein and in the appended claims, "interrogation
gate" refers to a device or group of devices that functions to (a)
send a signal to a tag in proximity to the device or devices to
induce the tag to transmit a tag identification signal, and/or (b)
to receive such tag identification signal from a tag in proximity
to the device or devices.
[0034] As used herein and in the appended claims, "response signal"
refers to a signal transmitted by a tag in response to a signal
from an interrogation gate.
[0035] FIG. 2 is a schematic plan view representation of an object
tracking system 200 in accordance with some aspects of the
invention.
[0036] The object tracking system 200 is installed, at least in
part, in a factory building 202. The system 200 includes tags 204,
represented in the drawing by small triangles. (The triangles may
also be considered to represent objects to which the respective
tags are affixed to permit tracking of the objects. The objects are
not separately shown.) In some exemplary embodiments, the factory
building 202 is employed for assembly of motor vehicles, and each
tag 204 is affixed to a respective vehicle that is being assembled
or has been assembled at the factory building 202. Although only a
few tags 204 are indicated for purposes of illustration in FIG. 2,
in practice the number of tags included in the system 200 may be in
the thousands. The tags may have features provided in accordance
with some aspects of the inventions, and are described in more
detail below.
[0037] The object tracking system 200 also includes interrogation
gates 106 and triangulation stations 108, which may be essentially
the same as, or generally similar to, the conventional items of the
same names discussed above in connection with FIG. 1. It will be
noted that the number of triangulation stations shown in FIG. 2 is
substantially less than the number shown in FIG. 1, notwithstanding
that the building 202 has substantially the same types of
obstructions 210 as the building of FIG. 1.
[0038] Also included in the object tracking system in accordance
with some aspects of the invention are antennas 212, which are
provided to receive from the tags 204 tag self-tracking position
information, as described in more detail below. Although not
separately shown, each antenna may have associated therewith
appropriate receive circuitry as well as a capability for buffering
data and relaying the data to a central (server) computer, which is
discussed below. Thus each antenna symbol 212 may be considered to
represent a receiver for receiving tag self-tracking position
information transmitted by tags 204.
[0039] FIG. 3 illustrates, in the form of a schematic plan view, an
alternative embodiment of the object tracking system 200, including
the factory building 202 shown in FIG. 2, together with an
associated parking, storage and/or testing lot 300. It will be
observed that the lot 300 has tags 204 of the object tracking
system present therein, and that antennas 212 of the object
tracking system are installed in the lot 300. Although not shown in
detail, it may be assumed that the factory building 202 is equipped
with system components as illustrated in FIG. 2.
[0040] FIG. 4 is a diagrammatic view of the object tracking system
200, showing additional system components. Thus, the system 200
further includes a server computer 400 which is coupled to the
interrogation gates 106, the antennas 212 and the triangulation
stations 108 via a tracking signal transmission network 402.
Details of the server computer 400 will be described below.
[0041] The system 200 also includes client computers 404 that are,
at least on occasion, coupled to the server computer 400 via a data
communication network 406. The client computers 404 may be, in some
embodiments, suitably programmed personal computers. The server
computer 400 and the client computers 404 operate such that the
client computers are able to retrieve from the server computer 400
and to display to users of the client computers information
regarding the current locations of objects to which the markers 204
are affixed.
[0042] Although the networks 402, 406 are shown as separate, the
two networks may be combined in some embodiments. Alternatively,
three or more networks may be employed in some embodiments and/or
point-to-point signal paths may be provided in some or all cases
between server 400 and other system components.
[0043] FIG. 5 is block diagram of a typical one of the tags 204, as
provided in accordance with some aspects of the invention.
[0044] The tag 204 includes a housing (schematically indicated at
500) which may contain all the other components of the tag 204.
[0045] The tag 204 may include appropriate circuitry to perform all
functions performed by the conventional tags 104 described above in
connection with the conventional object tracking system 100 of FIG.
1. Such circuitry is represented, in part, in FIG. 5 by a DTOA
transmit block 502 and an antenna 504 coupled to the DTOA transmit
block 502. The DTOA transmit block 502 may operate in accordance
with conventional practices to transmit, from time to time, via the
antenna 504, a triangulation signal that is suitable to be received
by the triangulation stations 108. Receipt of the triangulation
signal by three or more of the triangulation stations 108 allows
the server computer 400 to determine the current location of the
tag 204 by a conventional DTOA procedure. It will be understood
that the triangulation signal may include an identification code
that uniquely identifies the particular tag 204.
[0046] The block 502 and the antenna 504 may transmit the
triangulation signal at regular time intervals and/or in response
to a polling signal received by the tag 204. Accordingly the block
502 may include a capability (not separately indicated) for
receiving and responding to a polling signal. The polling signal
may be transmitted to the tag 204 by, e.g., one or more of the
triangulation stations 106.
[0047] Another portion of circuitry in the tag 204 that performs
conventional functionality is represented in FIG. 5 by an
interrogation signal receive block 506, a response signal transmit
block 508, and an antenna 510 that is coupled to the blocks 506,
508. The blocks 506, 508 and the antenna 510 may function so that
the tag 204 may interact, from time to time, with an interrogation
gate 106 to which the tag 204 is currently in proximity. That is,
the blocks 506, 508 and the antenna 510 may allow the tag 204 to
receive the interrogation signal from a proximate interrogation
gate and to transmit a response signal to the proximate
interrogation gate in response to receiving the interrogation
signal. It will be appreciated that the response signal may include
a tag identification code that uniquely identifies the tag 204.
This code may be the same as a code sent by the DTOA transmit block
502.
[0048] The blocks 506 and-508 may be constituted in some
embodiments by conventional RFID transponder circuitry. In some
embodiments, the antennas 504, 510 may be constituted by a single
antenna; similarly, there may be at least a partial overlap or
sharing of circuit components by the blocks 506, 508 on one hand
and the block 502 on the other hand.
[0049] The tag 204 further includes, in accordance with some
aspects of the invention, a self-tracking position module 512 by
which the tag 204 is able to track its own movement. The module 512
includes a plurality of sensors, indicated at 514, which may
include three or more acceleration sensors and/or at least one
angle or direction sensing device. The angle or direction sensing
device may, for example, function as a gyroscope. In some
embodiments, one or more of the sensors may have been fabricated by
use of conventional MEMS (micro-electro-mechanical systems)
technology on a semiconductor substrate or other suitable substrate
(not separately shown).
[0050] The module 512 also includes one or more analog-to-digital
converters 516 coupled to the sensors 514. The ADC(s) 516 function
to receive analog input signals from at least one of the sensors
and to convert the analog input signals into digital signals.
ADC(s) 516 may also effectively include digital data buffering
capabilities, which are not separately indicated.
[0051] Also included in the module 512 are a processor 518 and a
memory 520 that are coupled to the ADC(s) 516 via a data bus 522.
The processor 518 may, in some embodiments, be a conventional
microprocessor or microcontroller; alternatively the processor may
be constituted as processing circuitry that is part of a custom
circuit (e.g., an ASIC). The processor 518 may calculate, based on
input received from the sensors 514, changes in position
experienced by the tag 204. The memory 520 may function as a
program store for the processor 518 and as working memory, and may
also store data generated by the processor to indicate changes in
position of the tag 204. It may also include
pre-stored/pre-configured data, such as motion models.
[0052] The module 512 further includes a position data transmit
block 524 coupled between the processor 518 and an antenna 526. As
will be seen, the module 512 may transmit the position data
calculated by the processor 518 to one or more of the antennas 212
(FIGS. 2-4) via the position data transmit block 524 and the
antenna 526. The transmission from the module 512 may also include
the tag's unique identification code, which may be the same as the
code utilized for DTOA tracking and for interaction with
interrogation gates.
[0053] The module 512 also includes a reset block 528 which may be
coupled to the antenna 526 to receive a reset signal or other
relevant signal and to supply a corresponding input to processor
518 (via bus 522), so that processor 518 causes the position data
stored in the memory 520 to be cleared (reset) so that the
self-tracking function of the module 512 starts anew.
[0054] Further details of operation of the self-tracking position
module 512 will be described below.
[0055] Some portions of the module 512 may overlap and/or be shared
with other portions of the tag 204. For example, the antenna 526
may be the same as one or both antennas 504, 510. At least some of
the circuitry of position data transmit block 524 may be shared
with either or both of blocks 502, 508. Furthermore, the processor
518 may operate to provide some of the functionality of one or more
of blocks 502, 506, 508. The unique tag identification code
referred to above in connection with blocks 502, 508 may, in some
embodiments, be stored in the memory 520 and may be retrieved from
the memory 520 when needed for transmission as part of the
triangulation signal transmitted by block 502 and/or when needed
for transmission as part of the response signal transmitted by
block 508.
[0056] The tag 204 also includes a power supply 530 which is a
source of power for other electrical or electronic components of
the tag 204. In some embodiments the power supply 530 is
constituted at least in part by a battery. In other embodiments,
the power supply may be coupled to a power source outside of the
tag 204 to convert the external power for use by the tag
components. For example, if the object to which the tag is affixed
is a motor vehicle, the power supply 530 may be coupled (removably
or otherwise) to the vehicle electrical power system (e.g. to the
vehicle main battery). To simplify the drawing, connections between
the power supply 530 and other components of the tag 204 are
omitted.
[0057] FIG. 6 is a block diagram of the server computer 400. In
some embodiments, the server may, in terms of its hardware aspects,
be entirely conventional. The server 400 includes one or more
processors 600, which may be a conventional microprocessor or
microprocessors. Also included in server 400 are memory 602, one or
more communication interfaces 604, and input/output devices 606,
all of which are in communication with the processor 600. The
memory 602 may be, in some embodiments, one or more of RAM, ROM,
flash memory, etc., and may serve as one or more of working memory,
program storage memory, etc. The communication interfaces 604 allow
the server 400 to exchange data with the client computers 404 (FIG.
4) and to receive tag position information and/or input signals
from the interrogation gates 106, the triangulation stations 108
and the antennas 212. Command, status and control signals to and/or
from the interrogation gates 106, the triangulation stations 108
and the antennas 212 may also be exchanged with the server 400 via
the communication interfaces 604.
[0058] The I/O devices 606 may include one or more conventional
devices such as displays, printers, keyboards, a mouse, a
trackball, etc.
[0059] Also included in the server 400, and in communication with
the processor 600, is a mass storage device 608. Mass storage
device 608 may be constituted by one or magnetic storage devices,
such as hard disks, one or more optical storage devices, and/or
solid state storage. The mass storage 608 may store an application
or applications 610, by which the server 400 manages interactions
with the tags 204, and an application or applications 612, by which
the server 400 acts as a server with respect to client computers
404. There may also be stored in the mass storage 608 a database
614, in which an up-to-date record may be maintained of the current
and/or last known locations of all of the tags 204. The same or
another database may also store correspondences between tag
identifiers and object identifiers, if the objects are identified
by codes independent of the tag identification codes.
[0060] Operation of a typical one of the tags 204 will now be
described with reference to FIG. 7, which is a flow chart that
illustrates functions performed and/or overseen by the processor
518 (FIG. 5) of the tag 204. The functions indicated in FIG. 7
relate only to generating, storing and transmitting self-tracking
position data by the tag; the processor 518 and/or other portions
of the tag may also be operable to provide conventional
triangulation signals and/or to respond to interrogation gates, as
described in connection with FIG. 5 and elsewhere herein.
[0061] Initially in the process of FIG. 7, as indicated at 700, the
processor 518 may receive input signals from one or more of the
sensors 514 (FIG. 5). Such input may indicate acceleration of the
tag, for example, along one or more of three mutually orthogonal
axes of a frame of reference of the tag; in addition or
alternatively, such input may indicate a change of orientation of
the tag.
[0062] By double integrating the indicated acceleration input
signals, while also taking into account changes in orientation of
the tag, error models, and motion models, the processor 518 is able
to calculate positional displacements of the tag relative to a
given starting point, which may be established on the basis of a
reset event, as discussed below. On the basis of such calculations,
the processor updates the tag's self-tracking position data, as
stored in the memory 520 (FIG. 5), to reflect changes in the tag's
location. The calculation of self-tracking position data and
storage of updated self-tracking position data are indicated at 702
in FIG. 7.
[0063] Following 702 is a decision 704, at which the processor 518
determines whether a reset event has occurred. In some embodiments,
a reset event occurs when the tag receives a signal from the system
to indicate that the system has a fix on the tag's current
location. Such a location fix may come about as a result of any one
of the tag interacting with an interrogation gate, a successfull
DTOA operation with respect to the tag, or the system's accepting
from the tag the currently updated tag self-tracking position
data.
[0064] If a positive determination is made at 704, i.e., if it is
determined that a reset event has occurred, then the processor
resets (clears) the currently stored tag self-tracking position
data to indicate that the tag is now at a new starting point for
future self-tracking operation. The resetting of the stored
position data is indicated at 706.
[0065] A decision 708 follows 706, or immediately follows 704 if a
negative determination is made at 704. At decision 708, the
processor 518 determines whether it is time for the tag to transmit
the currently stored self-tracking position data. The timing of
transmission of the self-tracking position data may be at regular
time intervals timed by the tag and/or after a predetermined amount
of self-tracked movement of the tag and/or in response to an
interrogation signal from the system or may be when the object has
come to a standstill. If a positive determination is made at 708,
then the tag transmits a signal or signals to indicate the
identification code for the tag and the currently stored
self-tracking position data, as indicated at 710. The process of
FIG. 7 then loops back to 700. Alternatively, if a negative
determination is made at 708, the process loops back to 700 without
transmitting the self-tracking position data.
[0066] It should be understood that FIG. 7 and the above discussion
thereof do not imply a fixed order of performing the functions of
FIG. 7, and that such functions may be performed in any order that
is practicable.
[0067] Operation of the server computer 400 will now be described
with reference to FIG. 8, which is a flow chart that illustrates
some aspects of the tag interaction manager application 610 (FIG.
6) which runs on the server computer 400.
[0068] As indicated at 800, the following functions may be
performed for each tag 204, or at least for each tag that is
registered in an active status with the system.
[0069] In a decision at 802, it is determined whether a current
location for the tag in question can be determined by either a DTOA
process or by detection via an interrogation gate. If a positive
determination is made at 802, then, as indicated at 804, the server
computer determines the current location of the tag by using a
conventional DTOA procedure or based on the tag's interaction with
an interrogation gate, as indicated by a signal received by the
interrogation gate in question. (As a practical matter, 802 and 804
may be effectively combined. That is, a positive determination may
continue to be made at 802 as long as the server computer is able
to maintain an effective fix on the tag's current position using
DTOA or input from one or another of the interrogation gates.) Upon
the determination of the tag's current position at 804, the server
computer causes a reset signal to be sent to the tag, as indicated
at 806, to trigger a reset event at the tag. The reset signal may
be sent by any one or more of an interrogation gate 106, a
triangulation station 108 or an antenna 212 or by another broadcast
antenna or antennas, which are not shown. In some embodiments, the
tag may automatically reset or be reset upon interaction with an
interrogation gate, and without action of the server computer in
such cases.
[0070] If a negative determination is made at 802, i.e., if it is
determined that the tag's location cannot be determined by DTOA or
by interaction with an interrogation gate, then, as indicated at
808, the server switches into a mode in which it receives from the
tag, via one or more antenna 212, the tag self-tracking position
information that the tag has stored therein. Then, as indicated at
810, the server determines the current location of the tag based on
the tag self-tracking position information received at 808 and
based on the tag's last known position, as stored in the tag
location database 614 (FIG. 6), which may have been determined
based on any one of a DTOA procedure, interaction by the tag with
an interrogation gate, or previous use of tag self-tracking
position information by the server.
[0071] Following 810, the server may cause a reset signal to be
sent to the tag, as indicated at 806.
[0072] It should be understood that FIG. 8 and the above discussion
thereof do not imply a fixed order of performing the functions of
FIG. 8, and that such functions may be performed in any order that
is practicable.
[0073] The server may perform functions beyond those indicated in
FIG. 8. For example, the server may make the current tag locations
from the tag location database 614 available to the client
computers 404 upon request from the client computers 404, so that
users of the system may use the client computers to determine the
current locations of tags, and/or the current locations of objects
to which the tags are affixed. The tag location database 614 and/or
another database stored in the server or in one or more of the
client computers may indicate associations between particular tags
and the objects to which they are affixed.
[0074] In addition, the server may operate to permit tags to be
registered as active with the system or for tags to be removed from
active status. The server may also operate to allow associations to
be recorded between tags and objects to which they are affixed.
[0075] Since the system can switch between determining object
locations based on tag self-tracking information and other location
determining techniques, the system can reliably track objects with
reduced reliance on DTOA procedures. The number of triangulation
stations can be reduced, thereby lowering the cost of the system,
while only a relatively few antennas 212 may be required to receive
the self-tracking information from the tags. One advantage of the
use of the tag self-tracking information is that reflections of the
tag signals which contain the self-tracking information may aid in
allowing the signals to be received by the antennas 212. In
general, there may be considerable flexibility in the placement of
the antennas 212.
[0076] In other embodiments, the triangulation stations and DTOA
tracking of tags may be dispensed with entirely, in favor of
reliance on interrogation gates and tag self-tracking. This may
lead to reduced system cost, while still providing adequate object
tracking. In some embodiments, resetting of the tag self-tracking
information may occur only at interrogation gates. In addition, or
alternatively, the tag self-tracking information may be received,
in some embodiments, only at interrogation stations. In the latter
cases, tags may carry information allowing for historical tracing
and documentation of the movements of an object to which the tag is
attached.
[0077] In embodiments in which the tags are to store a record of
the movement of associated objects, resetting of the tag
self-tracking information may be omitted, or an active
self-tracking position information store may be reset without
resetting a historical movement information store in the tag.
[0078] In other embodiments, the self-tracking module of the tags
may operate to provide a current direction of movement of the tags.
This may be done in addition to or instead of tracking changes in
the tag's position. When a tag passes through an interrogation
gate, the information from the tag which indicates direction of
movement may be transmitted to the gate, so that the system may
detect in which direction the tag is moving through the gate. This
may make it unnecessary to provide two gates at each checkpoint, as
has been the conventional practice when it is desired to detect the
tag's direction of movement through the checkpoint.
[0079] In still other embodiments, DTOA tracking and tag
self-tracking are employed, but interrogation gates are
omitted.
[0080] Although the system has been described in detail in the
foregoing embodiments, it is to be understood that the descriptions
have been provided for purposes of illustration only and that other
variations both in form and detail can be made thereupon by those
skilled in the art without departing from the spirit and scope of
the invention, which is defined solely by the appended claims.
* * * * *